BAGHDAD (AP) – A bomb planted near a bridge in northern Baghdad killed five people on passing minibuses during rush hour Wednesday, Iraqi police said.

A woman and a 7-year-old boy were among the dead, and at least 10 other people were wounded in the mostly Shiite neighborhood of Hurriyah, an officer said on condition of anonymity out of security concerns.

Across town, two mortar rounds hit a busy street in the central Baghdad area of Karrada, killing a civilian and wounding five others, police said.

The U.S. military said it captured an Iranian-trained bomb expert Wednesday southeast of Baghdad during a raid on the man’s home.

The suspect is believed to have traveled to Iran several times for explosives training, and has numerous Iranian contacts who help him smuggle weapons and bomb-making materials into Iraq, according to a military statement.

U.S. troops, acting on intelligence from other criminals already in custody, subdued the suspect after he reached for a weapon, but no shots were fired, the statement said. It described the explosives expert as a member of a “special group” language the U.S. uses to describe Shiite militiamen defying a cease-fire order by anti-American cleric Muqtada al-Sadr. Many of them are believed to have fled recent fighting in his Baghdad stronghold of Sadr City.

An indefinite curfew was imposed north of Baghdad in Saddam Hussein’s home village of Ouja and police scoured the area Wednesday, after the killing a day earlier of the head of Saddam’s tribal clan.

Sheik Ali al-Nida and one of his guards died in an explosion Tuesday that Iraqi police blamed on a bomb that had been glued to the undercarriage of their car.

Al-Nida was chief of the al-Bu Nasir tribe, a large Sunni Arab clan with about 20,000 members, including Saddam’s family.

Another prominent sheik in the area, with whom al-Nida had joined forces in the past year to fight al-Qaida-inspired militants, said Wednesday an investigation committee had been formed to probe the killing.

Sheik Hamad al-Jubouri said investigators had ruled out any sabotage by al-Nida’s guards or relatives still loyal to the late deposed Iraqi dictator, and that he believed al-Qaida in Iraq was responsible.

Also Wednesday, a spokesman for former Washington insider and ex-deputy prime minister Ahmad Chalabi was quoted by an Iraqi newspaper as saying Chalabi would contest the country’s next elections. He scheduled a news conference for Thursday to announce a new parliamentary bloc, Azzaman newspaper reported.